BD Transduction Laboratories™ MAP Kinase Activation Sampler Kit

The family of serine/threonine kinases known as mitogen-activated protein kinases (MAP kinases) are activated after cell stimulation by a variety of hormones and growth factors, as well as during cell responses to stress. Three important kinases in this family include ERK1/2, JNK/SAPK1, and p38. These kinases all contain dual phosphorylation sites that mediate their activation. ERK1 and ERK2 (44/42 kDa) are Ser/Thr kinases activated in cells following stimulation with growth factors such as insulin, the platelet-derived growth factor, or the epidermal growth factor. In rat, these proteins are phosphorylated at Thr-202/Tyr-204 and Thr-183/Tyr-185, respectively. ERK1 and 2 have been implicated in growth factor signaling, as well as other signal transduction pathways. Growth factor stimulation leads to activation of Ras and Raf, leading to phosphorylation of MEK1 (MAPK/ERK kinase) which, in turn, activates ERK via dual phosphorylation. Thus, ERK1 and 2 are critical kinases in multiple signal transduction pathways that regulate cell growth and differentiation. External stimuli, like endotoxins, UV irradiation, heat, and hyperosmolarity, induce an array of cellular responses that culminate with gene expression, ultimately dictating an adaptation to the new environment. Stress signals activate both p38 and JNK/SAPK1 kinases. Activation of JNK/SAPK requires the phosphorylation of Thr-183/Tyr-185 by MKK4 and MKK7. Active JNK/SAPK phosphorylates other kinases and multiple transcription factors that induce expression of genes, such as proinflammatory cytokines. p38 MAP kinases include p38α, β, γ, and δ. Activation of p38 MAPK is mediated through phosphorylation of Thr-180/ Tyr-182 by MKK3, MKK4, and MKK6. This leads to the activation of multiple transcription factors (NF-κB, ATF-2, Elk-1, and CHOP) that induce expression of many different genes. Thus, these MAP kinases have important roles in many different signal transduction pathways where they regulate both cytoplasmic and nuclear proteins.